Half-sandwich RuII-[9]aneS3 complexes with dicarboxylate ligands: synthesis, characterization and chemical behaviorElectronic supplementary information (ESI) available: X-Ray structures (ORTEP) of compounds 2 and 5; packing arrangement of 3 in the solid state; time-evolution electronic absorption spectra of 2, 3, 5 and 6; time-evolution difference electronic absorption spectra of 1–6; absorbance/time spectra at selected wavelengths for 1–6; table of hydrolysis rate constants. Fig. S1–S8 and Table S1. See DOI: 10.1039/b707011j

With the aim of further developing the structure–activity relationship in biologically active half-sandwich Ru(ii)-[9]aneS3 complexes ([9]aneS3 = 1,4,7-trithiacyclononane), a series of new mono- and dinuclear complexes bearing the chelating dicarboxylate ligands oxalate (ox), malonate (mal) and methylmalonate (mmal), have been synthesized and studied. Treatment of the precursor [Ru([9]aneS3)(dmso)3][CF3SO3]2 (7) with equivalent amounts of K2(dicarb) afforded the corresponding neutral complexes with the general formula [Ru([9]aneS3)(dmso-S)(η2-dicarb)] (where dicarb = ox (1), mal (2) and mmal (3)), while using half an equivalent of K2(ox), the symmetric dimer [{Ru([9]aneS3)(dmso-S)}2(µ-η4-ox)][CF3SO3]2 (4) was isolated. The reaction of 7 with the oxalato complex fac-[Ru(dmso-S)3(dmso-O)(η2-ox)] (9) yielded two asymmetric dimers, namely [{Ru([9]aneS3)(dmso-S)}(µ-η4-ox){fac-Ru(dmso-S)3(CF3SO3)}][CF3SO3] (5) and [{Ru([9]aneS3)(dmso-S)}(µ-η4-ox){fac-Ru(dmso-S)3(dmso-O)}][CF3SO3]2 (6), depending on the reaction conditions. All new complexes were structurally characterized, both in solution (by NMR spectroscopy) and in the solid state (by X-ray crystallography). The chemical behavior of the complexes in aqueous solution was studied by UV-Vis and NMR spectroscopy in view of their potential antitumor activity: the monomers partially release a dmso ligand to yield the monofunctional aqua adduct [Ru([9]aneS3)(η2-dicarb)(H2O)], while the dimers rapidly open up the oxalato bridge to give two mononuclear fragments. Splitting of the asymmetric dimers 5 and 6 occurs selectively and the ox moiety remains bonded to the fac-Ru(dmso-S)3 fragment. A detailed comparison of the structural and chemical features of 1–6 with those of similar dicarboxylate complexes possessing the fac-Ru(dmso-S)3 fragment in place of Ru([9]aneS3) allows us to draw a number of general conclusions on the binding preferences of dicarb ligands on the octahedral Ru(ii) center. [ABSTRACT FROM AUTHOR]